1. Field of the Invention
The present invention relates to a surface-mount antenna for use in a mobile communication device (such as a mobile phone) and in a wireless local-area network (LAN). The invention also relates to a communication device using such a surface-mount antenna.
2. Description of the Related Art
A prior art surface-mount antenna is shown in FIG. 10. This antenna comprises a rectangular dielectric base 31 made of a ceramic, resin, or the like. A hole 32 extends through the base 31 between two opposite end surfaces of the base 31. A radiating electrode 32a is formed inside the hole 32. A capacitance loading electrode 35 is formed at a first end surface of the dielectric base 31 and connected with a first end of the radiating electrode 32a. A feeding electrode 33 is formed at the second end surface of the dielectric base 31 and connected with the second end of the radiating electrode 32a. Grounding electrodes 34a and 34b are formed on opposite sides, respectively, of the second end surface of the dielectric base 31.
In this prior art surface-mount antenna, the capacitance between the capacitance loading electrode 35 and each of the grounding electrodes 34a and 34b must be increased in order to accomplish miniaturization while permitting surface mounting. For this purpose, it is necessary to increase the dielectric constant of the dielectric base 31, which in turn increases the Q. As a consequence, the frequency bandwidth is narrowed. Furthermore, the prior art communication device on which the prior art narrow-band, surface-mount antenna is mounted is unable to sufficiently accommodate itself to frequency deviations caused by the human body and the enclosure of the device. Another disadvantage is that the input impedance of the antenna is uniquely determined by the size of the dielectric base and by the size of the hole extending through the base.